The following descriptions relate to a connection mechanism for connecting a plate member and a shaft member employed, for example, in an endoscope.
Generally, at an operation section of an endoscope, connection mechanisms such as a mechanism for operating a bending portion of an insertion section of the endoscope, a mechanism for changing a rising angle of a treatment tool and the like are provided. Such a mechanism employs a connection mechanism which connects the plate member with the shaft member such that the plate member does not rotate relative to the shaft member.
Typically, in such a connection mechanism, a portion of the shaft member is formed to have an outer-screwed portion. The outer-screwed portion is inserted through an opening formed on the plate member, and with use of a nut having an inner-screw, the plate member is secured to the shaft member. An example of such a configuration is disclosed in Japanese Patent Provisional Publication No. HEI 7-194519.
FIG. 10 shows an example of a conventional connection mechanism. As shown in FIG. 10, a shaft member 90 is formed with a polygonal column section 92 next to an outer-screw section 91. A plate member 93 is formed with a polygonal hole 94 to be fitted on the polygonal column section 92. The plate member 93 is fitted on the polygonal column section 92 and contacts a stepped portion 96 formed at the end of the polygonal column section 92, and urged toward the stepped portion 96 by fastening a nut member 95 provided with an inter-screw which engages with the outer-screw section 91.
Between the polygonal column section 92 and the polygonal hole 94, some play may occur in the rotational direction due to manufacturing errors. Because of such play, fastening of the nut member 95 with respect to the plate member 93 may be loosened in a certain period of time. In such a case, play may occur between the plate member 93 and the shaft member 90.
FIG. 11 shows another example of a conventional connection mechanism. In this example, the shaft member 90 is formed with a cylindrical member formed with an outer-screw, and both the plate member 93 and the nut member 95 engage with the outer-screw of the shaft member such that the plate member 93 and the nut member 95 are urged against each other.
Also in this structure, due to an external force applied to the plate member, the play may occur during usage of the connection mechanism.